Question

我有一个JCombobox，它从MySql表的列中获取数据。

  public void FillCombo1(){
  try {
    String sql = "SELECT `Expense Code` FROM `database`.`expense_code_master`";

    PreparedStatement pst = (PreparedStatement)conn.prepareStatement(sql);
    rs = pst.executeQuery();

    while (rs.next()) {
        String name = rs.getString("Expense Code");
        comboBox.addItem(name);
    }
    }catch (Exception ex) {
        System.out.println("Error: "+ex);
  }
}

现在我想从同一个表中获取一个值，该值与我在组合框中选择的值相关。我怎么能这样做？

Table schema:

Expense Code (primary key) | Account No (int)
E120                       | 12222

所以我想获取值（帐户编号）并将其与ActionListener放在JLabel中

Answer 1

您可以利用ItemListener来完成此任务。

JLabel myLabel = ... // Example JLabel from other part of program
...

class ItemChangeListener implements ItemListener{
    @Override
    public void itemStateChanged(ItemEvent event){ // Fired on selection
        if(event.getStateChange() == ItemEvent.SELECTED){ // Check for selection
            Object item = event.getItem(); // Here is selected item
            String expenseCode = item.toString(); // Get String

            String result = ...; // Use query here - 
                                 // same way as with your other query

            myLabel.setText(result); // Update JLabel with found String
        }
    }       
}

请务必将ItemChangeListener添加到JComboBox。

comboBox.addItemListener(new ItemChangeListener());

SQL查询将是这样的。

// expenseCode would be the String you got in the itemStateChanged method
String sql2 = "SELECT `Account No` FROM `database`.`expense_code_master` " + 
              "WHERE `Expense Code` == `" + expenseCode + "`";

通过选择ComboBox中的项目从MySql表中选择数据

1 个答案: